N, X = gets.split.map(&:to_i)
A = gets.split.map(&:to_i)
B = gets.split.map(&:to_i)
C = A.map { |a| a - X }
T = C.sum

if T >= 0
  puts 0
elsif C.max < 0
  puts -1
else
  L = T.abs
  dp = Array.new(L + 1, Float::INFINITY)
  dp[0] = 0

  C.each_with_index do |c, idx|
    next if c >= 0

    L.downto(0) do |i|
      ni = i + c.abs
      ni = L if ni > L

      n_cost = dp[i] + B[idx]
      dp[ni] = n_cost if dp[ni] > n_cost
    end
  end

  puts dp[T.abs..-1].min
end